求指导，sql优化的问题

Question

create index xxx1 on teacher_info(school,id);
create index xxxs on teacher_level(teacher_id,comment_id);
create index xxxd on teacher_comment(id);

Answer 1

索引情况如何，在条件字段上建立索引，
EXPLAIN　SQL语句，贴结果

Answer 2

首先谢谢回答，这个sql语句有索引，where条件后面的都有

Answer 3

贴出你的 show index from ..
explain select ...
不要贴图，直接贴文本以供分析。

Answer 4

哈哈，再次感谢诸位大大。1. show  index from teacher_info (这样看着比较乱，粘贴出去就好了)
Table      Non_unique   Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment
teacher_info 0   PRIMARY        1         id         A         913108                  BTREE
teacher_info 1   loveliness  1         loveliness A         6                  BTREE
teacher_info 1   schoolkey  1         school         A         915                  BTREE
teacher_info 1   nameKey  1         name         A         913108                          BTREE
teacher_info 1   departmentKey  1         department A         13233                          YES  BTREE
teacher_info 1   isShieldKey  1         is_shield A         6                          YES     BTREE
teacher_info 1   id          1         id         A         913108                           BTREE

Answer 5

2. show  index from teacher_level
Table       Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment
teacher_level 0        PRIMARY         1          id         A         3420069                  BTREE
teacher_level 1        user_id         1          user_id A         3420069                  BTREE
teacher_level 1        teacher_id 1         teacher_id A         3420069                  BTREE
teacher_level 1        commentkey 1         comment_id A         3420069                  BTREE

Answer 6

3. show  index from teacher_comment
Table         Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment
teacher_comment 0          PRIMARY 1         id         A          3369939         BTREE
teacher_comment 1          teacher_id 1         teacher_id A           3369939          BTREE
teacher_comment 1          user_id 1         user_id         A           3369939          BTREE
teacher_comment 1          schoolkey 1         school_id A           1131                 YES BTREE
teacher_comment 1          shieldKey 1         is_shield A             18                  YES BTREE

Answer 7

您好，之前我确实忘加联合索引了，抱歉，抱歉。但是我加上后，效果不太明显，麻烦您再帮我瞅瞅。
show  index from teacher_info 
Table          Non_unique  Key_name Seq_in_index Column_name Collation Cardinality
  Sub_part    Null   Index_Type  
teacher_info 0   PRIMARY  1  id        A 1016262 BTREE
teacher_info 1 loveliness 1 loveliness A 10 BTREE
teacher_info 1 schoolkey 1 school        A 4748 BTREE
teacher_info 1 nameKey         1 name        A 1016262 BTREE
teacher_info 1 departmentKey 1 department A 8262 YES BTREE
teacher_info 1 isShieldKey 1 is_shield A 10 YES BTREE
teacher_info 1 index_sii 1 school        A 2363 BTREE
teacher_info 1 index_sii 2 id        A 1016262 BTREE